The use of polyurethane dispersions in different fields is generally known. Different methods such as batch process or continuous process using a variety of equipments may be employed to produce such dispersions.
U.S. Pat. No. 6,720,385 discloses aqueous polyurethane latexes prepared from prepolymer formulations including a polyisocyanate component and polyol component, wherein from 5 to 40 percent of the weight of the polyol component is ethylene oxide in the form of ethylene oxide applied as an end cap onto a propylene oxide or higher oxyalkylene polyoxyalkylene polyol, and no more than 45 percent of the weight of polyol component is ethylene oxide.
U.S. Pat. No. 5,959,027 discloses a polyurethane/urea/thiourea latex having a narrow molecular weight polydispersity and sub-micron particle size, which is prepared by first preparing a high internal phase ratio (HIPR) emulsion of a polyurethane/urea/thiourea prepolymer, then contacting the emulsion with a chain-extending reagent under such conditions to form the polymer latex.
U.S. Pat. No. 5,688,842 discloses a method of preparing a high internal phase ratio emulsion without phase inversion comprising the steps of: a) continuously merging into a disperser and in the presence of an emulsifying and a stabilizing amount of a surfactant, a continuous phase liquid stream having a flow rate R1, and a disperse phase liquid stream having a flow rate R2; and b) mixing the merged streams with a sufficient amount of shear, and with R2: R1 sufficiently constant, to form the high internal phase ratio emulsion without phase inversion or stepwise distribution of an internal phase into an external phase; wherein R2: R1 encompasses a range, the lower limit of which range being defined by a point where the volume average particle size of the high internal phase ratio emulsion begins to show an inverse dependence on R2: R1, and wherein the upper limit of which range is just less than an R2: R1 where a phase inversion of the high internal phase ratio emulsion takes place.
U.S. Pat. No. 5,539,021 discloses a method of preparing a high internal phase ratio emulsion without phase inversion comprising the steps of: a) continuously merging into a disperser and in the presence of an emulsifying and a stabilizing amount of a surfactant, a continuous phase liquid stream having a flow rate R1, and a disperse phase liquid stream having a flow rate R2; and b) mixing the merged streams with a sufficient amount of shear, and with R2: R1 sufficiently constant, to form the high internal phase ratio emulsion without phase inversion or stepwise distribution of an internal phase into an external phase; wherein R2: R1 encompasses a range, the lower limit of which range being defined by a point where the volume average particle size of the high internal phase ratio emulsion begins to show an inverse dependence on R2: R1, and wherein the upper limit of which range is just less than an R2: R1 where a phase inversion of the high internal phase ratio emulsion takes place.
U.S. Pat. No. 4,742,095 discloses a continuous process for the production of aqueous polyurethane-urea dispersions by (a) mixing an emulsifiable isocyanate-terminated prepolymer with an aqueous medium in a low shear, stator-rotor dynamic mixer operating at a speed of about 500 to 8000 rpm utilizing a mixing wattage of about 0.3 to 10.0 watts/cubic centimeter and a mixing volume of at least about 0.1 liters, the average residence time of the aqueous medium and the prepolymer being about 1 to 30 seconds and the overall flow rate through the dynamic mixer being at least about 50 kg/h and (b) reacting the dispersed isocyanate-terminated prepolymer prepared in (a) with a polyamine chain extender to form an aqueous polyurethane-urea dispersion.
U.S. Patent Application Publication No. 2004/0242764 discloses a process for producing a polyurethane emulsion by emulsifying a urethane prepolymer, which contains substantially no organic solvent and also has at least two isocyanate groups per one molecule, with water and completing chain extension.
Despite the research efforts in developing more stable dispersions, there is still a need for an improved device to produce dispersions with optimum particle sizes, solid level contents, and reduced fouling; furthermore, there is still a need for an improved method of producing such dispersions.